Effect of foot core exercise and arch-supported insole on balance and vertical jump performance in football players with foot pronation

Abstract

Background

Football is a sport that requires both aerobic and anaerobic performance with dynamic movements. Lower extremity injuries are common, especially in the ankle and foot, where foot pronation is a frequent biomechanical issue that can impair balance and performance.

Objectives

This study aimed to evaluate the effects of foot core exercises and arch-supported insoles on balance and vertical jump performance in elite football players.

Methods

Thirty elite male football players with foot pronation deformity were randomly assigned to two groups: Insole Group (IG, n = 15), using only arch-supported insoles, and Insole + Exercise Group (IEG, n = 15), combining insoles with structured foot core exercises for four weeks. Assessments included Navicular Drop Test (NDT), Y-Balance Test, Flamingo Balance Test, Vertical Jump Test, and Visual Analogue Scale (VAS). Pre- and post-test comparisons were analyzed using paired t-tests or Wilcoxon tests, and time × group effects were examined with repeated measures ANOVA.

Results

Significant improvements were observed in both groups for NDT, balance, and vertical jump performance (p < 0.05). The IEG group showed superior gains in NDT and greater pain reduction. Additionally, vertical jump performance showed a near-significant trend favoring the IEG group (p = 0.059).

Conclusions

Combining structured foot exercises with arch-supported insoles results in better outcomes for balance, pronation control, and jump performance compared to insoles alone. These findings support incorporating foot-specific exercises into rehabilitation for footballers with pronation.

ClinicalTrials.gov NCT05821803

URL: https://clinicaltrials.gov/study/NCT05821803

Keywords

Foot pronation balance insoles exercise football players

Introduction

Football is among the most popular sports, with over 260 million active players worldwide.¹ It involves various movements such as running, jumping, passing, shooting, dribbling, turning, heading, and tackling.² Due to its dynamic and high-contact nature, football participation carries a significant risk of acute and chronic injuries among players of all ages and skill levels.³ Lower extremity injuries have steadily increased over the years.^4,5 The most frequently reported injury types were ligament sprains, muscle strains, and contusions, predominantly affecting the lower extremities, especially ankles and knees, due to sudden directional changes, impacts, and repetitive stress.⁶

Injury prevalence data indicate that the lower limbs are the most commonly affected area, with an estimated incidence rate of 6.8 injuries per 1000 h of participation.⁷ The most frequent lower limb injuries include ankle sprains, anterior talofibular ligament injuries, hamstring strains, shin splints, and Achilles tendon injuries, accounting for 70–93% of all injuries among male players.⁸

Several intrinsic and extrinsic factors contribute to injury risk in football players. Extrinsic factors include competition level, player skill level, use of ankle tape or braces, footwear type, and playing surface.⁹ Intrinsic factors involve player-specific characteristics such as previous injuries, age, sex, aerobic fitness, body composition, flexibility, limb dominance, muscle strength, balance, reaction time, posture, anatomical alignment, and foot morphology.⁹

Figure 1.

Flow chart of the study.

Among intrinsic factors, foot pronation is one of the most common biomechanical issues affecting football players.¹⁰ Proper foot alignment is crucial for lower limb movement and stability, and alterations in foot posture can significantly impact an athlete's performance.¹¹ Overpronation, in particular, induces biomechanical changes that increase stress on the foot and lower leg, reduce shock absorption, alter gait mechanics, and has been suggested to elevate the risk of injuries such as plantar fasciitis, shin splints, and stress fractures.¹² Beyond injury risk, overpronation negatively affects dynamic and static balance, lower limb power, and coordination, which are crucial for technical skills like shooting and rapid directional changes.^13,14

As balance plays a vital role in football performance, any instability caused by excessive foot pronation can hinder critical movements such as sudden accelerations, decelerations, and heading the ball. To mitigate these effects, medially placed insoles (MPI) are commonly prescribed to provide shock absorption, correct foot alignment, and optimize weight distribution.¹⁵ Additionally, foot core strengthening exercises have been recommended as an effective strategy for enhancing foot stability, improving neuromuscular control, and reducing overuse injuries.¹⁶

Although previous studies have investigated the effects of insoles and foot exercises separately, only limited research has examined their combined impact in football players. While some studies have reported beneficial outcomes,¹⁷ there remains a gap in the literature regarding the optimal use of personalized insoles together with targeted foot exercises for footballers with overpronation.

This study aims to examine the effects of foot pronation exercises and arch-supported insoles on balance and vertical jump performance among elite football players. We hypothesize that combining foot pronation exercises with insole use will result in greater improvements in balance and vertical jump test performance compared to insole use alone.

Methods

Study design

This randomized controlled study included 30 elite male football players with overpronated feet, recruited from a specialized center between June–July 2022. Participants were assigned to groups using block randomization (Figure 1 ).

Sample size

To determine the minimum sample size, the effect size was calculated using the pre- and post-intervention values of the main variables from a previous study group. This calculation was performed with G*Power version 3.1.9.7 (Heinrich-Heine-Universität, Düsseldorf, Germany). Based on the foot posture index data reported by Kim et al. (effect size = 1.95), at least six participants per group were required to achieve 80% power at a significance level of 0.05.¹⁸

Participants

Inclusion criteria were elite football players aged 18–35 years, navicular drop ≥10 mm, with at least one year of official league participation, and bilateral foot pronation deformity. Exclusion criteria were previous lower limb surgery, fractures, neurological conditions, acute lower limb injuries within the last three months, knee pathology, or vestibular disorders. The study was approved by Yeditepe University Ethics Committee (No:202203Y0193) and registered on ClinicalTrials.gov (NCT05821803), adhering to the Declaration of Helsinki guidelines.

Study protocol

Thirty elite football players meeting the criteria were randomly assigned (block randomization) into Insoles (n = 15) and Insoles + Exercise (n = 15) groups. Both groups received personalized insoles for four weeks, while the Insoles + Exercise group additionally performed foot pronation exercises twice weekly.

Outcome measures

Primary outcomes included the Navicular Drop Test (NDT), Y Balance Test, Flamingo Balance Test, and Vertical Jump Test; the Visual Analogue Scale was a secondary outcome. Tests were conducted bilaterally before and after four weeks of intervention.

Navicular drop test

The Navicular Drop Test (NDT) assessed foot pronation by measuring vertical displacement of the navicular tuberosity from sitting to standing positions in centimeters (cm) using a standard ruler; greater displacement indicated increased pronation.¹⁹ Each measurement was performed three times by the same physiotherapist, and the mean value was used to improve reliability.

Y balance test

The Y-balance test is a functional movement assessment to evaluate dynamic balance. It involves reaching in three different directions while standing on one foot at the center of a “Y” shaped pattern marked on the ground. Participants performed maximal limb reaches in anterior, posteromedial, and posterolateral directions while maintaining a single-leg stance. Distances were normalized by limb length (ASIS to medial malleolus) and expressed as a percentage.²⁰

Flamingo balance test

The static balance of football players was assessed using a cost-effective Flamingo Balance Test.^21,22 Participants stood on a beam (50 cm long, 5 cm high, 3 cm wide), balancing on their dominant foot. Once ready, external support was removed, and the timer began. Each loss of balance stopped the timer, which resumed after participants regained balance. The total number of balance losses in one minute was recorded.

Vertical jump test

The Vertical Jump Test measured players’ explosive anaerobic power. Participants stood adjacent to a wall, reaching upward to record initial fingertip height. They then performed maximal jumps from a 90-degree knee-flexed position. The highest of three attempts was recorded.²³

Visual analogue scale

We used the Visual Analogue Scale (VAS) to assess pain related to foot pronation deformity. We asked the football players to select the number according the level of pain. Football players reported their pain levels both before the intervention and after the four-week protocol. We asked the participants to choose a number that reflects their pain due to foot pronation between 0 and 10. While zero reflects no pain, ten reflects unbearable pain.^24,25

Interventions

Both groups used personalized insoles made at the Center for four weeks, and participants in the Insole + Exercise Group were also instructed to perform foot pronation exercises twice a week for four weeks under the supervision of a physiotherapist at the FootBalance Center. In the literature, 4 to 12-week protocols for addressing foot pronation are available.^26,27 Due to the intense training schedules of elite football players, we selected the minimum duration for our study.

Foot core exercise protocol

Short Foot Exercise contracts specific foot muscles to shorten the foot without flexing the toes and effectively engages intrinsic foot muscles to enhance the medial arch, thereby improving foot posture and stability. The exercise was done by asking participants to contract the foot muscles to shorten the foot in the anteroposterior direction without flexing the toes. The difficulty level was progressively increased through variations in sitting, standing, and half-squat positions.^28,29

The football players started with a 15-min exercise in the sitting position, then progressed to 7.5 min in sitting and standing positions, and eventually to 5 min in sitting, standing, and half-squat positions. We asked them to visually follow the movement and provided instructions throughout the exercise.

The towel curl exercise is used to strengthen the intrinsic muscles of the foot. The exercise included bunching up a towel using toes and was performed on a smooth surface. During the first two weeks, the exercise was done without load; in the following two weeks, a 2-kg dumbbell was placed on the towel to increase intensity. Participants performed the exercise three times per week, with three sets per session lasting about five minutes, for a total of four weeks.^30,31

The heel-to-toe raise exercise was done with the use of a tennis ball. This exercise specifically engages the Tibialis posterior muscle, which plays a crucial role in supporting the medial longitudinal arch of the foot. We asked football players to keep a tennis ball between their heels and maintain an upright posture. Then, we asked the participants to do heel rise while keeping the tennis ball. This exercise was done three times a week with 12 repetitions for four weeks.³²

Lastly, the tennis ball roll exercise involved rolling a tennis ball under the feet from toe to heel and applying pressure to the inner arch of the sole.³³ The exercise facilitates relaxation and relieves tension in muscles and fascia. The training consisted of every day per week and 5 min for each set.³⁴ During the training, we instructed the participants to focus their full attention and consciously feel the massage movements of the ball under their feet.

Insole preparation

Insole preparation involved using heated orthotic blanks (FootBalance Systems Ltd, Vantaa, Finland) to create a mold of the foot with neutral alignment, using the windlass mechanism with slightly flexed knees and dorsiflexed first metatarsophalangeal joint. The subjects were instructed to use their insole every day for approximately four weeks before performance test measurements to get accustomed to them.³⁵ The FootBalance 100% Control insole is designed for high-performance sports that require speed. This insole offers dynamic support and has a minimalist feel. It includes a shaped balance plate that provides strong support, and a narrow heel cup that relieves pressure, improves energy transfer, and adds space. The insole is extra thin, providing better contact with the ground and a better feel of the shoe on the foot. The toe area is wide enough to fit a variety of shoe widths. The 100% Control insole helps to distribute body weight evenly, which increases traction and accelerates movement.³⁶

Statistical analysis

Data were analyzed using SPSS version 25.0. The p-values presented in the tables for each group and measurement time point represent the within-group changes from baseline to the fourth week. For variables that did not follow a normal distribution, as indicated by skewness and kurtosis values outside the range of minus 1.5 to plus 1.5, non-parametric Wilcoxon signed-rank tests were employed. For normally distributed data, paired t-tests were conducted. Between-group comparisons, the main effects of time, and group × time interactions were analyzed using two-way repeated measures analysis of variance (RM-ANOVA). The group × time interaction was examined to determine whether time-dependent changes differed between groups. Since the assumptions of RM-ANOVA were not met for non-parametric variables, these analyses could not be performed. Instead, between-group differences in change scores (Δ) were compared using independent-samples Mann–Whitney U tests.

Results

General characteristics of participants

A total of 30 professional football players with bilateral foot pronation deformity were included in the study. Table 1 demonstrates that there were no significant baseline differences between the Insole and Insole + Exercise groups in terms of age, weight, height, and professional football experience (all p > 0.05).

Table 1.

Comparison of the sociodemographic parameters between study groups.

Variables	Insole	Insole + exercise	t	p-value (sig. 2-tailed)
Age (year)	23.67 ± 4.37	24.00 ± 4.30	−0.21	0.83
Weight (kg)	73.2 ± 7.22	74.1 ± 8.53	2.34	0.67
Height (m)	179.47 ± 7.10	175.20 ± 5.82	1.80	0.83
Professional football time (year)	9.67 ± 5.31	9.47 ± 5.05	0.10	0.91

Data expressed as mean ± standard deviation or number (percentage), m: meter, kg: kilogram.

Table 2 shows that no significant between-group differences were observed at baseline in navicular drop (right/left), Y-Balance Test (YBT) anterior (dominant/ nondominant), YBT posteromedial (dominant/nondominant), YBT posterolateral (dominant), Flamingo balance (dominant/nondominant), vertical jump height, or visual analogue scale (VAS) scores (independent-samples t-tests, all p > 0.05). The only exception was the YBT posterolateral on the nondominant limb, where a difference was detected (p = 0.011).

Table 2.

Comparison of performance test between groups at baseline.

Variables	Insole	Insole + exercise	t	p-value (sig. 2-tailed)
Navicular Drop Test Right (cm)	13.13 ± 1.55	12.93 ± 1.033	0.41	0.68
Navicular Drop Test Left (cm)	13.33 ± 1.29	12.60 ± 1.18	1.62	0.11
YBT Anterior Dominant (cm)	68.07 ± 3.05	68.80 ± 1.61	−0.82	0.418
YBT Anterior NonDominant (cm)	66.40 ± 3.13	67 ± 33	1.49	0.146
YBT PosteroMedial Dominant (cm)	99.67 ± 3.24	97.67 ± 2.76	1.81	0.08
YBT PosteroMedial Non-Dominant (cm)	97.40 ± 3.50	96.27 ± 2.68	0.99	0.328
YBT PosteroLateral Dominant (cm)	102.07 ± 3.61	100.20 ± 2.42	1.66	0.108
YBT PosteroLateral Non-Dominant (cm)	100.40 ± 4.08	99.53 ± 2.56	0.69	0 . 011
Flamingo Test Dominant	1.53 ± 0.91	0.93 ± 0.704	2.01	0.054
Flamingo Test Dominant	1.53 ± 0.91	0.93 ± 0.704	2.01	0.054
Vertical Jump Test (cm)	30.73 ± 2.31	1.53 ± 0.64	−1.76	0.089
VAS	6.07 ± 0.96	5.47 ± 0.83	1.72	0.082

Data expressed as mean ± standard deviation, p < 0.05 = statistically significant difference, YBT: Y Balance Test, cm: centimeter, VAS: Visual Analogue Scale.

Navicular drop test

Within-group comparisons between baseline and the fourth week are presented in Table 3. A significant main effect of time was observed for the Navicular Drop Test (NDT) on the right side (p < 0.001), with both groups demonstrating reductions after the intervention. A significant group effect was found (p = 0.021), but the group × time interaction did not reach significance (p = 0.104). On the left side, time effects were again significant (p < 0.001), while the group × time interaction approached significance (p = 0.063), suggesting a trend toward greater improvement in the Insole + Exercise group.

Table 3.

Comparison of tests within groups.

Variable	Group	Baseline	4 weeks	Δ	p	Group	Time	Group × Time/M-W*
Navicular Drop Test Right	Insole	13.13 ± 1.55	12.67 ± 1.67	0.46 ± 0.63	0.014	0.021	<0.001	0.021
	Insole + Exercise	12.93 ± 1.03	11.87 ± 0.99	1.06 ± 0.70	0.000
Navicular Drop Test Left	Insole	13.33 ± 1.29	12.87 ± 1.12	0.46 ± 0.51	0.008*			0.063
	Insole + Exercise	12.60 ± 1.18	11.80 ± 1.20	0.80 ± 0.41	0.001
YBT Anterior Dominant (cm)	Insole	68.07 ± 3.05	69.33 ± 2.79	1.26 ± 0.70	<0.001	0.393	<0.001	1.000
	Insole + Exercise	68.80 ± 1.61	70.07 ± 1.53	1.27 ± 0.96	<0.001
YBT Anterior Non-Dominant (cm)	Insole	66.40 ± 3.13	67.47 ± 2.97	1.07 ± 0.70	<0.001	0.267	<0.001	0.398
	Insole + Exercise	67.33	68.67	−1.34 ± 0.97	<0.001
YBT PosteroMedial Dominant (cm)	Insole	99.67 ± 3.24	101.20 ± 3.14	1.53 ± 0.74	<0.001	0.073	<0.001	0.828
	Insole + Exercise	97.67 ± 2.76	99.13 ± 2.87	1.46 ± 0.91	<0.001
YBT PosteroMedial Non-Dominant (cm)	Insole	97.40 ± 3.50	98.93 ± 3.19	1.53 ± 1.87	<0.001	0.388	<0.001	0.706
	Insole + Exercise	96.27 ± 2.68	97.27 ± 2.96	1.00 ± 2.10	0.087
YBT PosteroLateral Dominant (cm)	Insole	102.07 ± 3.61	103.67 ± 3.33	1.60 ± 0.82	<0.001*			0.740
	Insole + Exercise	100.20 ± 2.42	102.00 ± 2.44	1.80 ± 1.32	<0.001
YBT PosteroLateral Non-Dominant (cm)	Insole	100.40 ± 4.08	101.87 ± 3.75	1.46 ± 0.83	<0.001	0.520	<0.001	0.669
	Insole + Exercise	99.53 ± 2.56	101.20 ± 2.39	1.66 ± 1.58	0.001
Flamingo Test Dominant	Insole	1.53 ± 0.91	0.60 ± 0.82	0.93 ± 0.59	0.001			0.788
	Insole + Exercise	0.93 ± 0.704	0.07 ± 0.25	0.86 ± 0.74	0.004*
Flamingo Test Non-Dominant	Insole	2.07 ± 1.22	1.20 ± 0.94	0.86 ± 0.63	0.002	0.128	<0.001	0.517
	Insole + Exercise	1.53 ± 0.64	0.80 ± 0.41	0.73 ± 0.45	0.001
Vertical Jump Test (cm)	Insole	30.73 ± 2.31	32.00 ± 2.33	1.26 ± 0.59	<0.001	0.134	<0.001	0.059
	Insole + Exercise	32.07 ± 1.79	32.93 ± 1.58	0.86 ± 0.51	<0.001

Data expressed as mean ± standard deviation, p < 0.05 = statistically significant difference, YBT: Y Balance Test, cm: centimeter. *Mann-Whitney U test.

Balance tests

For the Y-Balance Test (YBT) anterior reach on the dominant limb, a significant main effect of time was found (p < 0.001), whereas neither the group effect nor the group × time interaction reached significance (p > 0.05). On the nondominant limb, significant improvements over time were also detected (p < 0.001), but again without group differences or group × time interactions (p > 0.05). Posteromedial reach (dominant and nondominant) improved significantly over time in both groups (p < 0.001). However, group and group × time effects were not significant (p > 0.05). Posterolateral reach of the dominant limb demonstrated significant improvements over time (p < 0.001), while the nondominant limb also improved significantly (p < 0.001), without between-group differences or interaction effects.

Flamingo test results also improved significantly on both dominant and nondominant limbs in both groups (p < 0.05 for time effect). No group or interaction effects were observed (p > 0.05).

Vertical jump test

Vertical jump performance increased significantly after four weeks in both groups (p < 0.001). A significant main effect of group was found (p = 0.014), but the group × time interaction was not statistically significant (p = 0.099).

Visual analogue scale

Changes in pain intensity measured with the Visual Analogue Scale (VAS) are presented in Table 4. Both groups demonstrated significant improvements after four weeks (insole: Δ = 2.0 ± 1.06, p < 0.001; insole + exercise: Δ = 3.0 ± 0.92, p < 0.001). A significant main effect of time was observed (p < 0.001), alongside a significant group × time interaction (p = 0.011), indicating greater pain reduction in the insole + exercise group.

Table 4.

Comparison of VAS score quality of life changes within groups.

Variable	Group	Baseline	4 weeks	Δ	p	Group	Time	Group × Time
VAS	Insole	6,07 ± 0,96	8,07 ± 0,59	2,0 ± 1,06	<0.001	0.645	<0.001	0.011
	Insole + Exercise	5,47 ± 0,83	8,47 ± 0,64	3,0 ± 0,92	<0.001

Data expressed as mean ± standard deviation, p < 0.05 = statistically significant difference, VAS: Visual Analogue Scale.

Discussion

The findings of this study revealed that a combination of structured foot exercise programs and insole decreased the amount of foot pronation and increased quality of life among professional football players having foot pronation deformity. Furthermore, after four weeks of intervention, the degree of foot pronation, balance, anaerobic performance, and pain were improved in football players in the Insole Group and Insole + Exercise Group.

These improvements can be attributed to both mechanical and neuromuscular mechanisms. Arch-supported insoles provide medial arch support and redistribute plantar pressure, thereby improving lower-limb alignment and reducing excessive pronation. In parallel, foot core exercises strengthen the intrinsic foot muscles, enhance proprioceptive input, and improve neuromuscular control of the medial longitudinal arch. Such adaptations may develop within a relatively short period, which may explain the functional improvements observed after only four weeks of intervention.

Regarding the Navicular Drop Test (NDT), significant reductions were observed on the dominant side in both groups. On the non-dominant side, improvements did not reach statistical significance, but a trend was detected (p = 0.063), suggesting that with larger sample sizes or longer intervention durations, significant between-group differences might emerge. In the literature, a study conducted on 14 university students showed that combining insole and short foot exercises three times per week for five weeks increased NDT distance compared to using an arch-supported insole.¹⁸ Similar to our study, Park et al. reported that short foot exercise was effective for NDT results among individuals with pes planus.³⁷ Moreover, Kim et al., found that applying short foot exercises was more effective than using arch support insole regarding medial longitudinal arch improvement and dynamic balance ability.¹⁸ Similarly, Hikawa et al. (2022) demonstrated that a 9-week arch support intervention improved foot morphology in young soccer players, highlighting the potential role of insoles in modifying pronation-related structures in football populations.³⁸ Consistent with the literature, insole, and exercise education combined further reduced foot pronation degrees in elite football players. Since an increase in pronation angle is associated with an increased risk of injuries in athletes, we may suggest that adding structured exercise training to the insole given to elite football players with pronation deformities may prevent injuries.³⁹

Another study finding showed that the football players’ dynamic and static balance was increased in both groups after four weeks of intervention. Additionally, the static balance score in the dominant lower extremity was higher in the Insole Group compared to the Insole + Exercise Group. The study by Moon et al., showed that short-foot exercises could improve Y-Balance Test scores even after one session in healthy adults with excessively pronated feet.⁴⁰ Another study on university students showed that combining an insole and short foot exercises increased Y-balance Test scores compared to using an insole.⁷ The study of Saeb et al. 2023, included 32 healthy cross-fit athletes divided into insole and control groups. The participants in the insole group used polyurethane insole for ten weeks, while the control group did not receive any intervention. They demonstrated that static and dynamic balance were increased at the end of the study in female participants in the insole group.⁴¹ Although the number of studies investigating the effects of insole, exercise, or a combination of elite athletes with overpronation deformity is limited, studies showed that increased foot pronation affects static and dynamic balance in football players compared to players with neutral foot posture.^42,43 Moreover, it is reported that football players use technical skills, such as passing, dribbling, shooting, and controlling the ball, which requires standing on one foot during a sportive performance. Similarly, balance plays a critical role in challenging situations such as when competing against an opponent, experiencing collisions, playing on slippery surfaces, dealing with sudden changes in the ball's direction, and remaining stable while in motion.^44–48 These findings are consistent with Moon et al.⁴⁰ and Saeb et al.,⁴² indicating that even relatively short interventions may improve balance parameters. The superior effect of the combined approach in our study suggests that passive support from insoles together with active neuromuscular adaptations from exercise provides greater functional benefit.

In the present study, we also showed that Vertical Jump Test scores were increased in both groups after four weeks of intervention. In the literature, studies involving athletes with foot deformities mainly focus on how insoles affect vertical jump performance, while studies investigating the effects of exercise on vertical jumping are limited. A study on 20 asymptomatic subjects with pronated feet showed that the six-week intrinsic foot muscle strengthening program did not change the vertical force on force palate assessment during the jump test.⁴⁹ Another study was conducted on 34 collegiate athletes to examine the effects of carbon-fiber shoe insole on athletic performance. They assessed the vertical jump performance of the athletes while wearing shoes with insole or without insole. The study demonstrated that wearing carbon fiber insole increased vertical jump distance compared to wearing regular athletic footwear among collegiate athletes.⁵⁰ Arastoo et al., also compared the vertical jump performance between flatfoot and healthy male amateur soccer players on a force platform. While athletes with flatfoot wear trainer shoes with insole, healthy ones wear trainer shoes. They showed that using the insole improved the stance time and take-off efficiency during the Vertical Jump Test.⁵¹ The vertical jump test is considered essential for football players due to its ability to assess lower body power and explosive strength. Specifically for football, vertical jump height and maximal strength levels have been reported as essential to heading performance in football players,⁵² Thus, regular use of the insole or a combination of insole and exercise training can improve vertical jump performance in elite football players with foot pronation.

Although our results did not show significant differences between groups, the improvement in both is consistent with Arastoo et al.⁵¹ and studies using carbon-fiber insoles.⁵² Moreover, the between-group comparison for vertical jump approached statistical significance (p = 0.059), indicating a potential trend favoring the combined intervention. This finding highlights that short-term interventions may produce early functional gains, but longer protocols could be required to detect robust between-group effects.

The study also showed that pain scores were statistically decreased in both groups, and VAS scores in the Insole + Exercise Group decreased more compared to the Insole Group. A meta-analyze showed that regular use of the insole and exercises reduces pain in adult flatfoot. Active interventions were more effective in reducing pain than passive ones.⁵³ Another study conducted on 17 recreational healthy team sports players showed that training insole could reduce pain and improve change of direction performance.⁵⁴ Channasanon et al. (2023) also found that using three medial arch supports reduced plantar heel pressure in healthy volunteers.⁵⁵ Besides that, a study conducted in the military with 1338 participants showed that the use of shock-absorbing insole reduced lower extremity overuse injuries.⁵⁶ Similarly, the FIFA-endorsed “The 11+” program was shown to enhance isokinetic lower limb strength in soccer players, supporting the role of structured neuromuscular training in injury prevention strategies.⁵⁷ Consistent with the literature our study showed that pain was reduced in both groups but the insole plus exercise group decreased VAS scores more compared to the insole group.

The study included a few limitations. The lack of only an exercise group can be considered as a limitation of the study. We could not find more elite football players with foot pronation deformity to participate in the study. Thus, we could not compare the outcomes from only the exercise group. In addition, we may consider that there is no follow-up period in the study as another limitation. We believe that studies with more elite football players and long-term follow-ups will contribute to the literature for future studies.

In conclusion, as far as we know this study is the first study that compared the effects of insole and a combination of structured exercise programs with insole among elite football players. Although pronation degree, balance test scores, vertical jump performance, and pain were improved in both groups, elite football players in the insole plus exercise group had more decrease in pronation degree and pain. We believe that foot core exercises to promote the foot muscles to retrain dynamically may increase muscle strength and reduce the degree of foot pronation. In addition, we may indicate that the improvement in the degree of foot pronation will continue not only when the athlete is using athletic shoes, but also while wearing a different shoe without insoles in daily life, so this may be the reason for reduced pain more in the exercise plus insole group. Thus, we conclude that elite football players should be assessed with a holistic approach and physiotherapists should advise not only performance-enhancing exercises and insoles but also structured exercise programs, including short foot exercises, towel curl exercises, and heel-to-rise exercises to elite football players with foot pronation deformity.

Footnotes

Authors’ contributions

Gizem Karadeniz: Study conception and planning, data collection, statistical analysis, result interpretation, literature review, manuscript drafting and formatting, final approval.

Assist. Prof. Elif Develi: Study supervision and planning, result interpretation, critical revisions, final approval.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

All authors have reviewed and approved the final version of the manuscript and agree with its submission to Isokinetics and Exercise Science.

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